Spinning wheels while up on stands

[PaulP38a]

This arvo I changed my off-road wheels back to on-road wheels and did it a little differently to last time. I used a 2.5T trolley jack to lift each end of the car and put 3T axle stands under, thereby having all 4 wheels off the ground.

Seemed to be a bit faster and easier on my back than doing one corner at a time. Would have been faster again if I'd bought a rattle gun last time I was down at SuperCrap, but I'm a bit wary of them rounding the heads of the wheel nuts.

Anyway, while the car was up in the air I did a little experiment and am wondering about the results.

Transmission in park, handbrake on...
Spin either rear wheel (either direction) and the opposite side spins in the other direction. I believe this rotation is normal on an open diff... but why did it spin with the transmission in park and handbrake on?
Same thing happens when I spin either of the front wheels.

Decided to get a llittle game and see what would happen with the motor running, in gear and handbrake off... ohh, nasty sounds like the ABS or TC crunching but the wheels did spin a bit.
With the handbrake on, the wheels still moved a little.

Not too keen to try that one again.

Maybe next time, I'll try engaging the rear air-locker with the engine off or at least out of gear. I think that both rear wheels would then move in the same direction. Does that sound right?

Cheers, Paul.

[Slunnie]

It sounds like everything is working perfectly. :lol2:

When you had the handbrake on, the ETC was trying to brake the front wheels to shunt power through to the rear which is the chatter you will have heard. The rears spinning a little is little bit of power that was shunted through the handbrake making it slip. It's not real good for the handbrake, but not the end of the world by any stretch of the imagination either.

Re the rear airlocker, that sounds correct... assuming the handbrake is off. If its on then you wont be able to spin the rear wheels at all.

[PhilipA]

Spin either rear wheel (either direction) and the opposite side spins in the other direction. I believe this rotation is normal on an open diff... but why did it spin with the transmission in park and handbrake on?
Same thing happens when I spin either of the front wheels.

This is correct for an open diff and is a by product of its design. With the input held all movement is via the planetary gears so one axle turns the other in the opposite direction.
Regards Philip A